Incomplete warm hemolysins. I. Case reports, serology, and immunoglobulin classes

Incomplete warm hemolysins (IWHs) form an independent class of red blood cell (RBC) autoantibodies. We studied eight sera in which autoantibodies with the characteristic features of IWHs were demonstrated. The case reports of those patients revealed that IWHs were predominantly associated with a serious course of autoimmune hemolytic disease. In four sera we found a combination of IWHs and cold agglutinins with the specificity anti-I. The cold agglutinins could be separated from the IWHs by affinity chromatography with immobilized I-active RBC material. The binding of IWHs to RBCs was demonstrated on the RBC surface with a modified enzyme-linked immunoassay (APAAP-EIA: monoclonal anti-immunoglobulin antibodies + bridging antibody + alkaline phosphatase/anti-alkaline phosphatase complexes). With the APAAP-EIA technique and different primary anti-immunoglobulin antibodies we found that seven sera contained IgM-IWHs and one contained IgG-IWHs. In three sera, IgM-IWHs with monotypical kappa light chains were detected.